Cellulosic material and process for its manufacture



Nov. 22, 1932. c, o zw 1,888,952

CELLULO SIC MATERIAL AND PROCESS FOR ITS MANUFACTURE FLled Oct. 23, 1950 QNVENTOR 0mm :5 flog/MP 7/;

BY ATTORNEY Patented Nov. .22, 1932 CHARLES HOLZWARTH, 0F PARLIN, NEW JERSEY C ELLULOSIC MATERIAL AND PROCESS FOR ITS MANUFACTURE Application filed October 23, 1930. Serial No. 490,806.

This invention relates to abrasion resisting film, particularly to film of cellulosic material, and to a method of making such a film.

A cellulose ester suitable for use as a support or base for light-sensitive photographic emulsions is known in the industry as film base. Film base is usually manufactured in an apparatus termed a casting unit in which the cellulose ester solution or film dope is poured-on the polished surface of a casting wheel upon which it is dried or hardened by heated air which drives off a portion of the solvents. When it is then stripped from the casting wheel, it is solidified in a continuous web or film. It is subsequently led over rollers and through a series of drying chambers that are incorporated in the casting unit where an additional portion of the solvents are driven off. When the film base is finally taken from the casting unit it still contains residual solvents that impart flexibility and toughness.

The common type of motion picture film which has a base of cellulose nitrate or cellulose acetate is susceptible to scratching. The scratches occur during processing and. projection, and are usually the determining factor in the life of the film. After a number of projections the scratches extend in long areas in the direction of the travel of the film in the projector and produce an undesirable efl'ect known as rain when the picture is projected on the screen.

Many kinds of treatments have been de-' scribed to remedy this trouble, such as waxes, oils, lacquers, and the like, applied to the manufactured film after processing. These treatments generally aim to make the film harder and therefore more resistant to abra- 0 sion, or they attempt to lubricate the film to reduce its coefiicient of friction.

I have found that it is not sufiicient merely to apply waxes in a molten state or in solu tion to the surface of the film. This merely produces a stratum of wax thereon which soon becomes smeary in service, accumulates on the projectorgate, or otherwise behaves undesirably.

Furthermore, it is obviously impractical to attempt to make the base hard enough to usual scratch on a dry or a thoroughly seasoned but untreated cellulose ester film, as Well as of a scratch on a film that has purposely been hardened by surface applications, reveals in both instances an extremely ragged edge formation in each scratch which obviously quite readily accumulates dust and grime n service and soon becomes opaque and obect-ionably apparent on the screen. I have also observed that a film not thoroughly seasoned and therefore containing residual solvents remains susceptible to abrasion, but the ragged edge formation of the scratches is diminished.

My invention aims to provide an improved anti-abrasion film base. A further object is to provide a process for making such film that will confine the residual solvents therein. Another object is to provide an anti-abrasion film base having a non-gumming or nonsmearing surface. Additional and more specific objects will plainly appear from the detailed description presented herein.

In the accompanying drawing, the figure diagrammatically illustrates an enlarged cross-sectional view of my improved abrasion-resistant film, comprising the base B and the surface impregnation W on each side thereof.

To enable those skilled in the art to use my invention I will as an illustration describe a preferred method of carrying it into effect, with the understanding that modifications may be made and the invention embodied in different forms without departing from its spirit and scope in its broader aspects.

My invention comprises the discovery that if waxes are applied by my method at a certain stage during the manufacture of the film base, a surface impregnation is obtained so that no perceptible film of wax is presented on the surface of the base, but all the valuable effects of lubrication are obtained and the film is kept tough, flexible and resistant to abrasion not only by the nature of the wax itself but also because it tends to confine the residual solvents within the film base.

l have also discovered that certain waxes not only reduce friction but they are inherently of the nature to permit only smoothedged evenly formed scratches when subjected to irresistible abrasion on the film.

ll first prepare a colloidal solution of a wax, preferably of carnauba wax, in alcohol. Suitable waxes similar to carnauba waxes are Japan wax, beeswax, and the synthetic waxes having similar characteristics. Such a wax is dispersed in amyl alcohol by grinding the wax in alcohol in a suitable mill. The ground and dispersed wax is then added to a mixture comprising approximately 66 parts of amyl alcohol and approximately 33 parts of ethyl alcohol, the resulting colloidal solution containing approximately one part wax.

A colloidal solution such as described above is then heated to a temperature not above the melting point of the wax used, in order to obtain a solution of completely dispersed wax. This heated solution is then applied to each surface of the heated unseasoned film base by immersion or by application rollers or in any other manner well known in the art.

In order to augment the penetration of the wax into the film base, when the solution is applied the film base should be at a temperaturel not above the melting point of the wax use The stage in the manufacture of the film base when it is in the preferred condition in which to apply thereto my improved solution is the period after the film base has been stripped from the casting wheel. At this stage the film base is in a green or unseasoned state and should be at the temperature not above the melting point of the wax. Furthermore, it then not only contains the desirable residual solvents, but it is also in its most receptive condition for the penetration thereinto of the heated wax solution. The finely divided wax under these conditions effectively penetrates or impregnates the surface of the film base in a manner that presents no apparent ultimate stratification of the wax on the finished film base thus coated.

While the preferred stage for the application of the solution has been described above, I have also found that the solution may be applied at any convenient period while the film base is being seasoned, providing the temperatures of the film base and the solution are not above the melting point of the wax used. After the application of the above described solution, subsequent drying or seasoning operations may be conducted if so desired at a temperature above the melting point of the wax in order to hasten its final seasoning, in any manner well known in the art.

The thus finished and seasoned film base or film of cellulosic material thus treated presents smooth and relatively hard lubricating ssaaea surfaces that are efiiciently abrasion resistant, resulting from my herein described improvements in the art, as the non-stratifying impregnation of wax therein effectively confines adequate residual solvents within the film base or the film of cellulosic material thus treated, and in addition incorporates therein a relatively hard finished surface that when subjected to irresistible abrasion permits any resulting scratches to have only a smooth-edged and even configuration that effectively diminishes the collection of foreign matter therein.

Having herein described a preferred embodiment of my invention, I do not desire to be limited thereto since it may be modified or embodied in different forms without departing from its spirit. It is expressly stated that this embodiment is illustrative only and that the invention is not limited to the materials, dimensions, and specific elements described, but comprises all the equivalents of the several cooperating features herein shown and described. Hence I desire to cover all forms and modifications within the language or scope of any one or more of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. The improvement in the art of treating cellulose ester photographic film base to make 'it resistant to abrasion, comprising applying thereto a heated colloidal solution of a wax in alcohol, said solution being applied while said base is heated and in its freshly cast, recently solidified state, and finally seasoning the thus treated base.

2. The method of confining residual solvents within cellulose ester film base to render it abrasion resistant, comprising heating said base while it is in an unseasoned condition, applying thereto a heated solution in alcohol of a Wax similar to carnauba wax; said solution and said base being heated during said application to approximately the melting point of said wax, and finally seasoning the thus treated base.

3. The improvement in the art of making abrasion resistant photographic film base, comprising applying a cellulose ester solution to a casting wheel combined in a suitable casting unit, removing a portion of the solvents from said solution by evaporation in a heated atmosphere, stripping from said casting wheel the thus heated and solidified web of film base, applying thereto a heated solution in alcohol of an impregnating wax, and finally SGZISOIliDg the thus treated film base.

4. The improvement in the art of treating cellulose ester film to make it resistant to abrasion, comprising heating said film while it is in an unseasoned condition, applying thereto a heated colloidal wax solution-containing approximately 66 parts of amyl alcohol, approximately 33 parts of ethyl alproximately one part of a wax similar to cara cohol and approximately one art of a wax similar to carnauba wax, and ally seasoning the thus treated film.

5. The improvement in the art of treating cellulose ester film to make it resistant to abrasion, comprising heating said film while it is in an unseasoned condition, applying thereto a heated colloidal wax solution containing approximately 66 parts of amyl alcohol, approximately 33 parts of ethyl alcohol and approximately one part of a mixture of waxes similar to carnauba wax, and finally seasoning the thus treated film.

6. The improvement in the art of treating cellulose ester film base to enable it to remain tough and flexible and to make it resistant to abrasion, comprising confining therein its residual solvents by first heating said base while it is in an unseasoned condition, im-

pregnating the surface thereof by applying thereto a heated colloidal solution contamlng approximately 66 parts of amyl alcohol, ap-

, port and a non-stratifying impregnation of wax in the surface thereof, said impregnation resulting from the application thereto and the subsequent drying therein of a heated solution of wax containing approximately 66 parts of amyl alcohol, approximately 33 parts of ethyl alcohol and approximately one part of a wax similar to carnauba wax.

11. An abrasion resistant transparent film base comprising a cellulose ester support containing residual solvents, and a non-stratifying surface impregnation of wax therein; 'sald impregnation presenting a smooth and relatively hard lubricating and abrasion resistant surface adapted to confine said residual solvents within. said'support and to prevent the uneven abrasion of said film base.

In testimony whereof, I have signed my name to this specification this 20th day of October, 1930.

CHARLES HOLZWARTH.

proximately 33 parts of ethyl alcohol and apnauba wax, said solution and said base being heated during said application to approximately the melting point of said wax, andfinally seasoning the thus treated film.

7. ljhe method of making abrasion resistant film base, comprising applying a cellulose ester solution to a casting wheel combined in a suitable casting unit, eliminating a portion of the solvents therefrom by evap-. oration in a heated atmosphere, stripping from said casting wheel the thus solidified and heated web of film base, applying thereto a heated solution of an impregnating wax,

said solution containing approximately 66 parts of amyl alcohol, approximately 33 parts of ethyl alcohol and approximately one part of a wax similar to carnauba wax, said solution and said base being heated during said application to approximately the melting point of said wax, and finally seasoning the thus treated film base.

'8. A photographic film base, comprising a support of cellulose ester containing residual solvents, and a non-stratifying and nonsmearing surface impregnation therein resulting from the application thereto and the subsequent seasoning therein of a heated wax solution in alcohol applied while said support was heated and in an unseasoned condition.

9. A film base comprising a cellulose ester support and a non-stratifylng impregnation of wax in the surface thereof resulting from the application thereto and the subsequent drying therein of a heated solution of a wax containing approximately 66 parts of amyl alcohol, approximately 33 parts of ethyl alcohol and approximately one part of a wax similar to carnauba wax.

10. An abrasion resistant and seasoned film base comprising a cellulose ester sup- 

